1. Field of the Invention
This invention relates to aqueous solutions or dispersions of special polyisocyanate polyaddition products which, by virtue of the choice of the polyhydroxyl compounds used for their production, are eminently suitable for use as adhesives, particularly for rubber, to a process for producing the aqueous solutions or dispersions and to their use as, or in the production of, adhesives.
2. Description of the Prior Art
Aqueous solutions or dispersions of polyisocyanate polyaddition products, i.e. aqueous solutions or dispersions of polyurethanes or polyurethane polyureas, are known. Their production is described, for example, in the following literature references: DE-PS No. 880,485, DE-AS No. 1,044,404, U.S. Pat. No. 3,036,998, DE-PS No. 1,178,586, DE-PS No. 1,134,946, DE-AS No. 1,237,306, DE-OS No. 1,595,602, U.S. Pat. No. 3,756,992, DE-OS No. 2,019,324, DE-OS No. 2,035,732, DE-OS No. 2,446,440, U.S. Pat. No. 3,479,310 and Angewandte Chemie 82, 35 (1970).
The known aqueous solutions or dispersions are suitable for a variety of applications, including inter alia the coating and bonding of any substrates. One disadvantage of the known solutions or dispersions lies in the fact that they are only suitable to a limited extent for bonding polymers, particularly rubber, to themselves and to other materials.
The aqueous solutions or dispersions described in DE-OS No. 2,804,603 and in EP-OS No. 3521, which were specifically developed as adhesives for rubber, are also not entirely satisfactory in that respect.
Accordingly, an object of the present invention is to provide new aqueous solutions or dispersions of polyisocyanate polyaddition products which are more suitable as adhesives for any substrates, particularly for rubber materials, than the solutions or dispersions of the prior art.
Surprisingly, this object is achieved by the solutions or dispersions according to the invention which are described in detail hereinafter and by the process according to the invention for their production. Bonds formed with the solutions or dispersions according to the invention, especially rubber-to-rubber bonds and bonds joining rubber to other materials, show separation strengths which exceed practical requirements, so that the bonded materials often cannot be separated without tearing.